# US 2022/0045686 A1 · High-pass shaped dither in continuous-time residue generation systems for analog-to-digital converters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0045686 A1 - Document ID: US20220045686A1 - Status: Published application - Kind: A1 - Application number: 17/390,852 - Filed: 2021-07-30 - Published: 2022-02-10 - Earliest claimed: 2020-08-07 - Assignees: Analog Devices International Unlimited Company - Applicants: Analog Devices International Unlimited Company - Inventors: Victor KOZLOV; Donald W. PATERSON; Sharvil Pradeep PATIL; Hajime SHIBATA - Web page: https://patentgrep.com/patent/US20220045686A1 ## CPC - H03M 1/0639: {using dither, e.g. using triangular or sawtooth waveforms (for increasing resolution H03M1/201)} - H03M 1/0641: {the dither being a random signal} - H03M 1/0626: {by filtering} - H03M 1/164: {the steps being performed sequentially in series-connected stages (H03M1/161 takes precedence)} - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract Mechanisms for reducing or eliminating a quantization error caused by a quantizer of a continuous-time (CT) residue generation system are disclosed. In particular, systems and methods described herein are based on using a dither generation and injection circuit that can perform a high-pass filtering of the additive dither signal (i.e., a high-pass shaped dither signal). Using high-pass shaped dither signals is expected to improve quantizer linearity without significantly reducing the available error correction range. The applied dither may be particularly effective at minimizing signal-dependent distortion in ADC output spectrum caused by the quantizer when the quantization error cancellation accuracy may be insufficient. ## Claims ### Claim 1 A continuous-time residue generation stage, comprising: a dither sequence generator to output a digital dither sequence; a dither signal processing part to receive the digital dither sequence and output a spectrally-shaped analog dither signal; a forward path having a continuous-time filter to receive an analog input signal; a feedforward path having a quantizer to receive the analog input signal and a digital-to-analog converter to receive a digital output of the quantizer, the quantizer having a node to sum the spectrally-shaped analog dither signal and the analog input signal; and a filter to receive a residue signal, the residue signal based on an output signal of the forward path and an output signal of the feedforward path. ### Claim 2 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the spectrally-shaped analog dither signal has an amplitude of one quantizer step of the quantizer, and a substantially uniform probability density function. ### Claim 3 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the spectrally-shaped analog dither signal has an amplitude of two quantizer steps of the quantizer, and a substantially triangular probability density function. ### Claim 4 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the spectrally-shaped analog dither signal is a high-pass shaped dither signal, and the filter has a low-pass filter response. ### Claim 5 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither sequence generator is a 1-bit pseudorandom binary sequence generator. ### Claim 6 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither sequence generator comprises a linear feedback shift register with storage elements. ### Claim 7 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither sequence generator comprises multi-bit pseudorandom sequence generator. ### Claim 8 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither sequence generator comprises two 1-bit pseudorandom binary sequence generators outputting two 1-bit pseudorandom binary sequences respectively, and the dither signal processing part comprises a node to sum two analog dither signals converted from the two 1-bit pseudorandom binary sequences to form the spectrally-shaped analog dither signal. ### Claim 9 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither sequence generator comprises 2-bit pseudorandom binary sequence generator outputting a 2-bit pseudorandom binary sequence, and the dither signal processing part comprises a node to sum two analog dither signals converted from respective bits of the 2-bit pseudorandom binary sequence to form the spectrally-shaped analog dither signal. ### Claim 10 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither signal processing part comprises: a zero-order-hold circuit to receive the digital dither sequence and output an analog dither signal; and an analog filter to receive the analog dither signal and output the spectrally-shaped analog dither signal. ### Claim 11 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither signal processing part comprises: a digital filter to receive the digital dither sequence and output a spectrally-shaped digital dither signal; and a digital-to-analog converter to receive the spectrally-shaped digital dither signal and output the spectrally-shaped analog dither signal. ### Claim 12 (depends on 1) The continuous-time residue generation stage of claim 1, further comprising: a digital filter to receive the digital dither sequence and output a filtered digital dither signal; and circuitry to subtract the filtered digital dither signal from the digital output of the quantizer. ### Claim 13 (depends on 12) The continuous-time residue generation stage of claim 12, wherein the filtered digital dither signal is spectrally-shaped by the digital filter in an equivalent manner as the spectrally-shaped analog dither signal. ### Claim 14 (depends on 1) The continuous-time residue generation stage of claim 1, wherein the dither signal processing part comprises: inverters to receive the digital dither sequence and output an analog dither signal; and an analog filter having capacitive and resistive components to receive the analog dither signal and output the spectrally-shaped analog dither signal. ### Claim 15 A continuous-time residue generation stage, comprising: a dither sequence generator to generate a digital dither sequence; a dither signal processing part to filter the digital dither sequence and generate a spectrally-shaped analog dither signal; a forward path to delay an analog input signal; a feedforward path having a quantizer and a digital-to-analog converter, the quantizer to sum the spectrally-shaped analog dither signal and the analog input signal, and to quantize the summed spectrally-shaped analog dither signal and the analog input signal; and a filter to filter a residue signal generated from outputs of the forward path and the feedforward path. ### Claim 16 (depends on 15) The continuous-time residue generation stage of claim 15, the dither signal processing part implements scaling to generate the spectrally-shaped analog dither signal having a predetermined amplitude. ### Claim 17 A method to reduce spurs caused by quantization error in a continuous-time residue generation stage, comprising: in a forward path, delaying an analog input signal; in a feedforward path, injecting a spectrally-shaped analog dither signal at an input of a quantizer, quantizing a summed spectrally-shaped analog dither signal and the analog input signal, and generating a reconstructed version of the analog input signal based on the quantizing; generating a residue signal based on the delayed analog input signal and the reconstructed version of the analog input signal; and filtering the residue signal. ### Claim 18 (depends on 17) The method of claim 17, further comprising: removing a further spectrally-shaped analog dither signal from the feedforward path after the quantizing. ### Claim 19 (depends on 17) The method of claim 17, further comprising: shaping a dither signal away from pass-band frequencies of the filtering of the residue signal to generate the spectrally-shaped analog dither signal. ### Claim 20 (depends on 17) The method of claim 17, further comprising: scaling a dither sequence or a dither signal to generate the spectrally-shaped analog dither signal having a predetermined amplitude.